Closed circuit breathing apparatus



Dec. 20, 1966 J. B. MCDONOUGH CLOSED CIRCUIT BREATHING APPARATUS Filed 001'.. 21. 1963 Ew m TR Hwawwm N United States Patent O 3,292,617 CLOSED CIRCUIT BREATHING APPARATUS John B. McDonough, McCandless Township, Pa., assignor to Mine Safety Appliances Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 21, 1963, Ser. No. 317,467 5 Claims. (Cl. 12S-142) This invention relates to breathing apparatus in which the circuit normally is closed, and more particularly to the breathing bag contained Iin such a circuit.

In closed circuit breathing apparatus Va breathing mask is connected with an air purifying canister and with a 'breathing bag that expands and contracts as the user breathes. One of the objections to such apparatus is that it requires considerable effort to use it because it requires work to expand and collapse the bag, and the entire system oiers resistance to flow of the air stream. Over a prolonged period the increased breathing effort that is necessary can become quite fat-iguing.

It is among the objects of this invention to provide breathing apparatus in which breathing is essentially resistance-free, in which the breathing bag is expanded and contracted mechanically, and in which the system is purged periodically t remove nitrogen from it. Another object is -to provide such Vappara-tus, which under certain conditions will automatically convert itself into pressure breathing apparatus.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which PIG. 1 is a diagram of the breathing apparatus, with the breathing bag shown in section; and

FIG. 2 is an enlarged cross section of the blower-control v-alve.

Referring to FIG. 1 of the drawings, a breathing mask 1 of any well known construction has a combined inlet and outlet provided with a T-tting 2, to which flexible inhalation and exhalation tubes 3 and 4 are connected. The fitting also includes inhalation and exhalation valves 5 and 6, so that the flow of air through the tubes is always in the s-ame direction. 'The inlet end of the inhalation tube is connected to a conduit 7 that is connected to the outlet end of an air purifying canister 8 of well known construction, which may contain KO2 for removing carbon dioxide and generating oxygen. Or, a chemical, such as LiOH, may -be used that will only remove the carbon dioxide. In such a case, oxygen will be supplied in -a manner that is described later. The conduit 4may be provided with an electric blower 9 to help reduce resistance to ow in the system, in which case valves 5 and 6 will insure proper ow if there is a power failure.

The outlet end of the exhalation tube 4 is connected to a conduit 11 that leads to the inlet end of canister 8, where it also is connected by a conduit 12 to the side of another conduit 13 secured to a breathing bag housing 14. Although the housing `may be provided with both an inlet and an outlet, it is preferred to com-bine the two into one opening 15, to which conduit 13 is connected. Disposed inside the housing and sealed to its wall around the inlet-outlet opening, is the open end of a exi-ble breathing bag 16. Preferably, the bag is provided with annular pleats or corrugations to increase its flexibility as much as possible. It will be seen that when -the wearer of the mask exhales, the exhaled air will be directed into the bag, which will therefore expand toward the bottom of the housing. During inhalation, air is withdrawn from the bag and passes through -the canister where it is purified lbefore it returns to the mask. During inhalation, the bag collapses upwardly in the housing.

It is a feature of -this invention that means is provided for mechanically expanding and contracting the bag so Patented Dec. 20, 1966 that substantially no effort will be required by the user for that purpose. Accordingly, a coil spring 20 is mounted in the ybag for normally holding it expanded. At the termination of inhalation, during which the spring is compressed by the collapsing bag, the spring will expand in the bag so that no work is required on the part of the user to expand the bag. In fact, -the expanding bag will tend to withdraw air from the lungs. While the bag is expanding, air escapes from the bag housing through a ice lnormally open electrically operated valve 21 connected to a second outlet 22 from the housing.

To mechanically collapse the bag during inhalation, the bag housing is provided with a second inlet 24, through which the housing is pressurized in order to exert air pressure against the outside of the bag and thereby cause it to move upwardly in the housing and force air out of itself through opening 15 and into the lungs of the wearer of the mask. The pressurizing may be done by any type of compressor at the second inlet, but preferably by a centrifugal blower 25 that forces air into the housing faster than it can escape through valve 21, whereby the air pressure around the bag is increased. Since the housings should ibe pressurized in this manner only during periods of inhalation, means are provided for periodically stopping the application of air pressure to the housing. With a continuously operating blower, this preferably is done by a valve that shuts olf the ow of air from the blower to the housing. The valve is controlled by the exhalations of the wearer of the mask in such a manner that the valve will be closed at the beginning of each exlhalation to permit the spring 20 to expand the bag without resistance from air pressure in the housing.

A suitable valve for this purpose is the well known Hawk valve, which has a body 27 provided with a large central passage 28 (FIG. 2) connected with the outlet of the blower. As `shown in FIG. 2, the end of the passage farthest from the blower is encircled by a valve seat 29, against which a closure member 30 is pressed by Imeans of a coil spring 31 compressed between it and a flexible diaphragm 32, the edge of which is clamped in a surrounding cup 33 spaced by spacers 34 from the valve body. During inhalation, air pressure from the blower forces the closure member olf its seat -and the air therefore flows out between the Valve body and the diaphragm cup and into the bag housing to collapse `the bag. However, When the user exhales, the air pressure is increased in a static tube 33a that connects the mask with t-he outer end of the diaphragm cup 33. This pressure clauses the diaphragm and spring to hold the closure on its seat and thereby shut ott communication between blower 25 and the inside of the bag housing 14.

It will therefore be seen from the description thus far that exhalation actually is aided by the expanding coil spring in the bag, and inhalation is aided by the increased air pressure in the housing around the bag, which forces the |bag upwardly toward a collapsed position. As a result, this apparatus olfers no resistance to breathing. It requires no effort on the part of the user to expand the collapse the bag.

In case an oxygen-generating chemical is not used in the canister, or if oxygen leaks from the system or an unusually large breath is taken during inhalation, the bag will collapse completely and open a valve in an oxygen make-up line 35. Thus, the upper wall of the housing may be provided with an inlet port 36 that normally is closed by a spring-pressed valve 37 having .a stem 38 extending down into the bag. When the bottom of the bag rises high enough to push upward on this stem, the valve is opened and oxygen will ilow through the port into the bag to expand the bag until the valve closes again. The make-up line is connected to an oxygen pipe 39 extending from a pressure regulator 40, the inlet of which is connected to a suitable supply of oxygen under pressure, such as a number of oxygen tanks 41. The pipe between the pressure regulator and the tanks maybe provided with a pressure operated electric switch 42 that will close when the pressure in the pipe falls below a predetermined value.

vWhen the switch closes, it tires an oxygen candle 43 that is connected with the tanks -to build up the pressure again for a short period of time.

After oxygen has been added to the system through valve 37, the bag may be fully expanded at the next exhalation. When that occurs, -the excess pressure is vented from the system by a check valve in the bag. Thus, the bottom of the bag is provided with an outlet 45 that normally is closed by a spring-pressed valve 46. This valve has a stem 47 that projects from the outlet and which will engage the bottom of the housing just before the bag is fully expanded. This will stop the downward movement of the valve but, as the bag continues to expand, the valve will open and allow excess air `to escape into the housing and out through valve 21. The oxygen pipe 39-also is connected through a normally closed electrically operated valve 50 to an aneroid controlled flow regulator 51, the outlet of which is connected into the system, such as into conduit 7. This valve is opened at predetermined intervals of time, such as about every half hour, by means of an electric timer 52. When the valve is opened, oxygen is delivered to the system to purge it, the excess gas causing the bag to fully expand and thereby open check valve 46 so that the system will be ushed out through housing valve 21.

Another feature of this invention is that this apparatus 4automatically is converted into a pressure breathing system when the ambient pressure falls below a predetermined value, such as when this apparatus is used in aircraft yat high altitudes. When a predetermined :altitude is reached at which the desired pressure in the system otherwise would be lost, -an altitude switch 54 closes and short circuits timer 52 by closing a relay 55 connected around the timer, so that oxygen valve 50 opens and remains open. Since the Vincreased pressure thus produced in the system closes blower valve 27 and would normally expand the bag to its full length and thereby cause the check valve in its bottom to open and allow the oxygen to escape, the altitude switch simultaneously closes the outlet valve 21 to seal the bag housing. At the same time, the altitude switch opens a normally closed electrically voperated valve 56 at the outer end of conduit 13 connected with the bag housing opening 15. As it is necessary to prevent the oxygen in the system from flowing out of the system through this vent valve as fast as it enters through the regulator, a pressure regulating valve 57 is mounted in conduit 13 in front of the vent valve for maintaining the desired pressure in the system. Only when that pressure is exceeded does oxygen escape through the vent.

Pressure regulating valve 57 may be -any valve that can be Yadjustably loaded to prevent'it from opening until a predetermined pressure in conduit 13 is reached. However, it is preferred to use a valve, the loading on which is varied automatically with the Variations in opening of oxygen regulator 51 with'altitude. Such a valve may be like blower valve 27, in which case the valve 57 is connected by a static tube 58 with the outlet of regulator 51. Therefore, as the regulator opens wider as higher altitudes are reached, the pressure in the static tube increases and consequently it requires more pressurel in thesystem -to open valve 57 before gas canescape through that valve and vent valve 56.

I claim:

1. In closed circuit breathing apparatus, a breathing mask, a breathing bag, a housing containing the bag and having an inlet and outlet communicating with the inside of the bag, conduit means connecting the mask with said inlet and outlet to permit breathing into and out of the bag, a spring inside the bag normally maintaining it exthe inside of the bag, means connected with the second inlet for periodically pressurizing the housing to collapse the 1 bag during periods of inhalation from the bag, the housing having a second outlet for escape of air pressure therefrom between said inhalation periods to permitthe spring to expand the collapsed bag, said bag having a portion provided with anopening movable toward and away from a wall of said housing, a valve normally closingsaid bag opening and having a member projecting therefrom engaging said housing wall when the bag approaches full expansion to open the valve, a normally open valve for said second outlet, a normally closed'valve having an outlet in communication with said trst-mentioned inlet, an oxygen supply line connected to the inlet of said lastmentioned valve, and means for opening the last-mentioned valve and closing said norm-ally `open valve.

2. In closed circuit breathing apparatus, a breathing mask, a breathing bag, a housing containing the bag and having an inlet and outlet communicating with the inside of the bag, conduit means connectingy the m'ask with said inlet and outlet to permit breathing into and out of the bag, a spring inside the bag normally maintaining it exi panded, the housing having a second inlet isolated from the inside of the bag, means connected with the second inlet for periodically pressurizing the housing to collapse the bag during periods of inhalation from the bag, the housing having a second outlet for escape of air therefrom between said inhalation periods to permit the spring to expand the collapsed bag, a normally closed valve having an outlet in communication with said first-mentioned inlet, an oxygen supply line connected to the inlet of said normally closed valve, said apparatus being provided with an outlet connecting the inside of the bag to atmosphere, a normally closed valve for said atmosphere outlet, means for opening said vnormally closed valves, and means for maintaining -a predetermined oxygen pressure in the bag while said atmosphere outlet is open.

3. In closed circuit breathing apparatus, a breathing bag, a housing containing the bag and having an inlet and outlet communicating with the inside of the bag to permit breathing into and out of the bag, a spring inside mask, an air purifying canister, breathing conduits connecting said mask and canister with said bag inlet and outlet, the housing having a second inlet isolated fromthe inside of the bag, means connected with the second inlet for periodically increasing the air pressure inside the housing to collapse the bag during periods of inhalation at said mask, means con-trolling said first-mentioned means responsive to increase in air pressure in the mask during exhalation between said inhalation periods for rendering said irst-mentioned means ineffective, the housing having a second outlet for escape of air therefrom to permit the spring to ex-pand the collapsed bag during exhalation at the mask, a normally open valve for the second outlet, said bag having a portion movable toward and away from a wall of said housing and provided with an opening, a spring-pressed valve normally closing said opening and having a stem projecting therefrom engaging said housing wall when the bag approaches full expansion to open the valve, a normally closed valve having an outlet connected with one of said conduits, an oxygen supply line connected to the inlet of said last-mentioned valve, and means responsive to a predetermined low ambient pressure for opening the last-mentioned valve and closing opening said vent valve While said normally open valve is closed, and means for maintaining a predetermined oxygen pressure in the bag while -the vent valve is open. 5. In closed circuit breathing apparatus, a breathing mask, a breathing bag, a housing containing the bag and having an inlet and outlet communicating With the inside of the bag, a conduit connecting the mask with said inlet and outlet to permit breathing into and out of the bag, a spring inside the bag normally maintaining it expanded, the housing having a second inlet and an open second outlet isolated from the inside of the bag, means connected with the second inlet for forcing air into the housing faster than it can escape through said second outlet in order to pressurize the housing to collapse the bag, and means 10 References Cited by the Examiner UNITED STATES PATENTS 2,269,500 1/ 1942 Wildhack 12S-202 X 2,902,992 9/ 1959 Renvall 12S-29 3,021,839 2/1962 Marsh 128-142 3,068,857 12/ 1962 -Black 128-29 3,101,708 8/ 1963 Perry et al 128-29 FOREIGN PATENTS 894,345 3/ 1944 France.

RICHARD A. GAUDET, Primary Examiner.

W. E. KAMM, Assistant Examiner. 

1. IN CLOSED CIRCUIT BREATHING APPARATUS, A BREATHING MASK, A BREATHING BAG, A HOUSING CONTAINING THE BAG AND HAVING AN INLET AND OUTLET COMMUNICATING WITH THE INSIDE OF THE BAG, CONDUIT MEANS CONNECTING THE MASK WITH SAID INLET AND OUTLET TO PERMIT BREATHING INTO AND OUT OF THE BAG, A SPRING INSIDE THE BAG NORMALLY MAINTAINING IT EXPENDED, THE HOUSING HAVING A SECOND INLET ISOLATED FROM THE INSISE OF THE BAG, MEANS CONNECTED WITH THE SECOND INLET FOR PERIODICALLY PRESSURIZING THE HOUSING TO COLLAPSE THE BAG DURING PERIODS OF INHALATION FROM THE BAG, THE HOUSING HAVING A SECOND OUTLET, FOR ESCAPE OF AIR PRESSURE THEREFROM BETWEEN SAID INHALATION PERIODS TO PERMIT THE SPRING TO EXPAND THE COLLAPSED BAG, SAID BAG HAVING A PORTION PROVIDING WITH AN OPENING MOVABLE TOWARD AND AWAY FROM A WALL OF SAID HOUSING, A VALVE NORMALLY CLOSING SAID BAG 